Particle Size Distribution Analysis for Ceramic Pot Water filter production

Maria del Mar Duocastella and Kai Morrill

Potters Without Borders, Enderby, British Columbia, Canada – September 2012

Abstract: To develop a standard Particle Distribution Analysis testing protocol for use in Ceramic Pot Water Filter factories.

Introduction: Ceramic Pot Water filters are generally manufactured from sources of raw clay that vary in their consistency, some factories have begun using particle distribution analysis to qualify clay batches, as well as for blending multiple clay sources in order to maintain a more homogeneous clay body. In order to promote common testing methods between factories, we have begun herein to develop testing protocols that utilize widely available apparatus and materials. It is desirable to develop an effective test that is easily accessible to individuals with limited laboratory experience. This test must be able to be performed in extremely rudimentary conditions with limited resources while presenting reliably accurate results. We hope that by establishing stabilized testing standards specific to filter production the test data will be useful in comparing clay bodies between all participating filter factories. We find that difficulties in ensuring that identical lab equipment is used (cylinder dimensions) may make it difficult to accurately compare results across different factories. Several standards already exist for soil classification; particles can be classified into categories of Clay, Silt or Sand. These categories are demarcated recognizing that suspended particle size is in direct relationship to settling time. For our purposes, we established a baseline for classification by comparing other standards and examining the results of our tests.

Although it is useful for general comparisons to define the samples by the three categories (Sand, Silt, Clay), for the purposes of detailed clay sample comparison, it is better to collect data from various particle sizes, thus developing a curve of particle size distribution. For this reason we tested samples at 13 different time intervals: 30 seconds, 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, and 24 hours. Having this expanded range of sample data allows us to compare samples in greater detail. These times were also chosen in order to complete the test within an 8 hour work day. *Note 1: Samples in Appendix 2 (Raw Data) which fall outside the standard testing procedure (Those prepared 24 or 48 hours before testing) were excluded from the final averages as there was significant variation in their results. It would have been interesting to use the results gathered to compare particle distribution results to burnout mixture ratios used in the participating factories. This proprietary information did not receive specific approval prior to publication.

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